The present invention relates to a method and apparatus of manufacturing a stator. More particularly, the present invention relates to an automated method of shielding, grouping, and splicing stator leads prior to lacing of the leads and the stator coil end windings.
Induction motors typically include a stator and a rotor. The stator includes a metallic core with a plurality of coils or windings running through the core. An alternating current is passed through these coils to generate an alternating magnetic flux field. The rotor has a plurality of coils or windings in which an alternating current is induced by the alternating magnetic flux field of the stator. The end coils or end turns of the stator are grouped together at axial ends of the stator and are often laced or stitched together to prevent their interfering with other components of a device. The end turns are often coated with an epoxy or resin subsequent to stitching. This coating helps reduce movement of the wires and provides an insulated barrier between the wires and other objects. Lacing in this case helps assure that the coils are tightly grouped together prior to coating.
Also extending from axial ends of the stator are several groups of bare wire leads. The leads serve to supply electrical power and control signals to the stator during operation. Because each of the leads carry signals of varying electric potential, the leads are typically insulated from one another with a non-electrically conductive shield or sleeve, respectively. The non-electrically conductive sleeve provides the leads with protection from shorting one another out in the event two or more leads happen to cross. During manufacture of the stator, placement of the sleeves on each lead is done manually by an operator on the manufacturing floor. More particularly, the operator initially retrieves pre-cuts sleeves and then manually threads each lead through its respective sleeve thereby providing the needed insulation. Additionally, because the length of many of the leads often is often not satisfactory to accomodate the lacing process, threaded extension leads are generally spliced to each of the stator leads. In order to splice a lead to an extension lead, an operator typically positions a connecting end of the lead and extension lead within a cramping tool which then completes the splicing procedure. Manual sleeving and splicing of each lead wire is tedious, time consuming, and involves ongoing operator involvement during the stator manufacture cycle.
As part of the manufacturing process, each stator is introduced to a station at which lacing thereof occurs. Use of a stator coil lacing machine avoids many of the manual operations otherwise necessary for lacing or stitching stator end coils and thus reduces labor costs and increases productivity and quality. At the lacing station, an operator typically lifts the stator and places the stator on the lacing machine. The lacing machine generally includes a worktable having a cylindrical arbor protruding upward from a central portion of the worktable. The arbor serves to facilitate proper placement of the stator on the lacing machine and aids in rotating the stator as lacing takes place. Once lacing is completed, the stator is lifted off the arbor and removed from the lacing machine and placed back on the pallet. The longer the longitudinal length of the arbor, the more effort that is required to place the stator thereon and remove the stator therefrom. Insertion and removal of the stator from the arbor is especially difficult given the oftentimes substantial weight of each stator which includes a heavy metallic core. While use of a lacing machine provides advantages in lacing the stator coils, the need to physically move the stator from the conveyer belt pallet to the lacing machine and back again to the pallet is a tedious process which impedes the overall manufacturing process.
One characteristic of some stator coil lacing machines is that the leads of the stator coil windings must be manually held and moved during lacing of the coils of the stator. Typically, a stator includes several groups of leads for supplying power and other signals to the stator. The leads must be held and moved in order to appropriately position the leads with respect to one or more lacing needles of the stator coil lacing machine. Oftentimes the leads are manually moved and positioned such that a portion of each lead is stitched to the coil in a desired manner. This allows the leads to extend from the stator at a desired location rather than loosely falling at random positions. The desired location from which the leads extend is often caused to correspond to openings in the stator housing which provide the leads with access outside the housing. Thus, one or both of the hands of the operator of a stator coil lacing machine is/are often preoccupied in positioning the leads during lacing of the coils of the stator. This has the disadvantages of preventing the operator from performing other tasks during stator coil lacing and thus lowers his or her productivity. In addition, an operator needs to be cautious of mistakenly coming in contact with the moving components of the stator coil lacing machine such as the lacing needles.
Therefore, what is needed is a method and apparatus for manufacturing a stator which minimizes the amount of manual intervention needed so as to overcome the shortfalls discussed above and others.
Briefly, a method and apparatus for automating the manufacturing process of a stator is provided. The stator includes a metal core with conducting wires oriented axially through the metal core. The conducting wires are grouped together into end windings which converge at upper and lower ends of the metal core. A series of leads extend from the upper and lower ends of the metal core and provide the stator with electrical control and power signals.
During manufacture, the stator is moved through a series of manufacturing stations in which a sequence of automated steps are performed to the stator at each of the stations. In particular, the present invention provides for the stator to be introduced to a first station in which the leads of the stator are automatically shielded or sleeved in order to electrically isolate the leads from one another. The stator is then moved to a second station where the leads are automatically grouped according to a predefined criteria. Following grouping, the stator is moved to a third station where a selected set of leads are automatically spliced to extension wires to allow a proper length of each lead wire to extend from the stator following the lacing procedure. Finally, the stator is moved to a lacing station where both the end windings and leads are automatically laced according to a predefined lacing protocol.
Automated processes which occur at each of the stations are performed while the stator is situated on a rotatable support such as a pallet having a rotating assembly disposed therein. The rotatable support is moved from station to station via a conveyer belt or the like and allows the stator to be automatically rotated to various positions at each station. Further, at each of the first, second, and third stations, a robotic arm is used to facilitate placement and positioning of the leads. The robotic arm may, for instance, be controlled by a central computer which controls the robotic arm to perform certain predefined tasks. Thus, using a combination of the robotic arm and the rotatable support, the present invention substantially reduces the amount of time operators need to spend at each of these stator manufacturing stations and increases the overall speed, accuracy, and efficiency at which such steps are performed.
According to one particular aspect of the present invention a method of shielding a lead of a stator as the stator is situated on a pallet is provided. The method includes the steps of selecting the lead by a first robotic device and positioning a sleeve over at least a portion of the lead by a second robotic device.
According to another aspect of the present invention, a system for manufacturing a stator is provided. The system includes a pallet including a base portion, a first ring rotatably disposed within the base portion for supporting the stator, and a second ring rotatably disposed in the base portion, the second ring including a plurality of clips for releasably securing a plurality of leads extending from the stator. The system further includes a conveyer system for supporting the pallet and moving the pallet between a plurality of stations and a means for sleeving at least one of the plurality of leads of the stator at one of the plurality of stations.
According to still another aspect of the present invention, a method for grouping a plurality of leads of a stator situated on a pallet is provided. The pallet includes a rotatable assembly having a plurality of lead securing devices. The method includes the steps of positioning one of the plurality of leads secured to a first of the plurality of lead securing devices to a predetermined position, removing the one of the plurality of leads from the first of the plurality of lead securing devices, rotating a second of the plurality of lead securing devices to the predetermined position, and securing the one of the plurality of leads to the second of the plurality of lead securing devices.
According to yet another aspect of the present invention a system for grouping leads of a stator is provided. The system includes a pallet having an inner rotatable ring for supporting the stator and an outer rotatable ring with a plurality of lead securing devices. The system further includes a means for removing at least one of the leads from one of the plurality of lead securing devices and placing the at least one of the leads into another of the plurality of lead securing devices.
According to yet another aspect of the present invention a method of splicing a lead of a stator to an extension lead is provided. The method includes the steps of positioning by a first robotic device the lead of the stator to a crimping tool, positioning by a second robotic device the extension lead to the crimping tool, and splicing by the crimping tool the lead to the extension lead.
To the accomplishment of the foregoing and related ends, the invention then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.